Sort an array of arrays in JavaScript

Question

I'm trying to sort an array of arrays with integers inside, for example:

var array = [[123, 3], [745, 4], [643, 5], [643, 2]];

How can I sort it in order to return something like the following?

array = [[745, 4], [643, 2], [643, 5], [123, 3]];

Answer 1

You can pass a custom comparison function to Array.prototype.sort(), like so:

var sortedArray = array.sort(function(a, b) { return a - b; });

This would sort an array of integers in ascending order. The comparison function should return:

• an integer that is less than 0 if you want a to appear before b
• an integer that is greater than 0 if you want b to appear before a
• 0 if a and b are the same

So, for this example you would want something like:

var sortedArray = array.sort(function(a, b) {
  return b[0] - a[0];
});

If you wanted to sort on both elements of each sub-array (ie. sort by the first element descending, then if they are the same then sort by the second element descending), you could do this:

var sortedArray = array.sort(function(a, b) {
  if (a[0] == b[0]) {
    return a[1] - b[1];
  }
  return b[0] - a[0];
});

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort for more info.